Given the difficulty in observing high redshift galaxies, we may ask which
aspects of the formation process we can see in the nearby universe. Ongoing
mergers of spiral galaxies provide unique laboratories for a study of the
physics of encounters, and they have been modeled in detail by various authors
(52,
53,
157,
334).
The current simulations
are very successful in reproducing most observables, and can be used to
constrain the orbits and halo properties of the merging galaxies. The end
results of these encounters are expected to resemble bright elliptical
galaxies
(15,
17).

One of the most interesting aspects of investigations of this type is that
they may result in a better understanding of the gas dynamics and star
formation during the encounter. Hernquist has shown that gas can be driven
into the centers of galaxies during the encounter
(156). This
provides a natural mechanism for nuclear starbursts and/or nuclear activity.
The gas masses and star formation rates in starbursts can be quite high, and
these events may be typical of the events that formed the stars in most
galaxies.